1. Field of the Invention
The present invention relates to a polymer electrolyte and a lithium battery using the same, and more particularly, to a polymer electrolyte having effective leakage resistance, and a lithium battery using the polymer electrolyte.
2. Description of the Related Art
Lithium secondary batteries using liquid electrolytic solutions use an organic solvent having a low boiling point to enhance low-temperature performance. However, the use of a low-boiling point organic solvent may give rise to swelling of an electrode assembly or the case of a pouch battery that is allowed to stand at high temperature, resulting in deterioration of reliability and safety of the battery under a high temperature condition.
To overcome these problems, a method of using solid polymer electrolytes has been proposed. Using solid polymer electrolytes reduces the danger of leakage of an electrolytic solution, thus increasing improved safety of a battery, unlike in the case of using liquid electrolytes.
However, using solid polymer electrolytic solutions decreases ionic conductivity compared to the case of using liquid electrolytes. Thus, in order to practically use solid polymer electrolytes in lithium secondary batteries, research must focus on solid polymer electrolytes having high ionic conductivity and effective electrochemical stability.
Linear polymers or crosslinkable polymers of homopolymers or copolymers basically having ethylene oxide are generally used as monomers of ionically conductive polymers for forming the solid polymer electrolytes.
However, the polymers formed from such monomers are susceptible to crystallization, so that the characteristics at low temperature are less effective. Also, since ethylene oxide has a strong affinity to an electrolytic solution, the polymers may move with the electrolytic solution by interaction between the electrolytic solution and the polymer chains decreasing the mobility of lithium ions.
To overcome the above-described problem, a multi-functional acrylate base compound is used in the manufacture of a polymer electrolyte.
However, such a multi-functional acrylate based compound has low polarity so that it exhibits low compatibility with a liquid electrolytic solution, forming a non-homogenous gel. Low compatibility between a monomer and an electrolytic solution reduces leakage resistance. A lithium battery using the polymer electrolyte with low leakage resistance has considerably reduced reliability.